F response in vascular and degenerative upper motor neuron lesions.
The F response represents the recurrent discharge of a small percentage of the motoneuron pool activated antidromically by any single impulse delivered to the nerve. We studied F waves from median nerve stimulation in 22 controls, in 30 patients with spasticity after cerebrovascular accident (CVA), and in 4 patients with familial spastic paraplegia (FSP). The following parameters were analyzed: median nerve conduction velocity, median nerve M response amplitude (M), average amplitude of 16 F responses (F16); persistence of F response (Fp) defined as the percentage of measurable responses to 16 stimuli, average amplitude of F response expressed as percentage of maximal M amplitude: (F16/M%). Results showed that Fp, F16 and F16/M% values were significantly increased on the spastic side of CVA patients and in FSP. Our findings indicate that after upper motor neuron lesions (whatever etiology and course) a change in the frequency of recurrent discharge and/or in the total number of lower motor neurons capable of backfiring occurs. Therefore, F response reflects the hyperexcitability state of the lower motor neurons in spasticity.
Uncini
A
A
Institute of Clinical Neurology and Sciences of Behavior, University of Chieti, Italy.
Cutarella
R
R
Di Muzio
A
A
Assetta
M
M
Lugaresi
A
A
Gambi
D
D
D000293:Adolescent; D000328:Adult; D000368:Aged; D002561:Cerebrovascular Disorders / Q000150:complications / Q000503:physiopathology; D004594:Electrophysiology; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009046:Motor Neurons / Q000502:physiology*; D009410:Nerve Degeneration / Q000502:physiology*; D009422:Nervous System Diseases / Q000503:physiopathology*; D009431:Neural Conduction / Q000502:physiology